Theorem on the Distribution of Short Time Single Particle Displacements

The distribution of the initial very short-time displacements of a single particle is considered for a class of classical systems with Gaussian initial velocity distributions and arbitrary initial particle positions. A very brief sketch is given of a rather intricate and lengthy proof that for this class of systems the nth order cumulants behave as t^{2n} for all n>2, rather than as t^{n}. We also briefly discuss some physical consequences for liquids.Comment: Short 8 page pedagogical review of cond-mat/0505734 for Proc. of "News, Expectations and Trends in Statistical Physics", Crete 200

Determinants of caregiving experiences and mental health of partners of cancer patients

BACKGROUND. Research regarding informal caregiving showed considerable individual variation in responses to cancer caregiving. The current longitudinal study examined determinants of caregiver outcomes in terms of caregiver experiences at 3 months and caregiver's mental health at 6 months after hospital discharge. It included both negative and positive dimensions of caregiving outcomes.METHODS. One hundred forty-eight patients with newly diagnosed colorectal carcinoma and their partners were included. Caregiver experiences were assessed by the Caregiver Reaction Assessment Scale, which contains four negative subscales (disrupted schedule, financial problems, lack of family support, and loss of physical strength) and one positive subscale (self-esteem). The mental health of the caregiver was assessed in terms of depression and quality of life. Possible determinants of the caregiver's experiences and mental health were categorized according to characteristics of the caregiver, the patient, and the care situation. Caregiving experiences were studied as a fourth additional category of possible determinants of the caregiver's mental health.RESULTS. Each domain of the caregiving experience was explained by different factors, with total explained variances ranging between 11-46%. Negative caregiver experiences were associated with a low income, living with only the patient, a distressed relationship, a high level of patient dependency, and a high involvement in caregiving tasks. Caregivers with a low level of education and caregivers of patients with a stoma were able to derive more self-esteem from caregiving. Although caregiving may lead to depression, especially in those experiencing loss of physical strength, caregivers may sustain their quality of life by deriving self-esteem from caregiving.CONCLUSIONS. It is important that professionals involved in the ongoing care of cancer patients and their families be aware of the increasing demands made on caregivers and the specific problems and uplifts they perceive in caregiving. Professional caregivers are urged to involve informal caregivers with care explicitly and continuously. However, specific attention to those caregivers who live only with the patient, those with a low income, those with a distressed relationship, and those with a high level of patient dependency and care involvement is warranted. Cancer 1999;86:577-88. (C) 1999 American Cancer Society.</p

All-photochemical rotation of molecular motors with a phosphorus stereoelement

Unidirectional molecular rotation based on alternating photochemical and thermal isomerizations of overcrowded alkenes is well established, but rotary cycles based purely on photochemical isomerizations are rare. Herein we report three new second-generation molecular motors featuring a phosphorus center in the lower half, which engenders a unique element of axial chirality. These motors exhibit unusual behavior, in that all four diastereomeric states can interconvert solely photochemically. Kinetic analysis and modeling reveal that the behavior of the new motors is consistent with all-photochemical unidirectional rotation. Furthermore, X-ray crystal structures of all four diastereomeric states of two of these new motors were obtained, which constitute the first achievements of crystallographic characterization of the full 360° rotational cycle of overcrowded-alkene-based molecular motors. Finally, the axial phosphorus stereoelement in the phosphine motor can be thermally inverted, and this epimerization enables a “shortcut” of the traditional rotational cycle of these compounds

Theorem on the Distribution of Short-Time Particle Displacements with Physical Applications

The distribution of the initial short-time displacements of particles is considered for a class of classical systems under rather general conditions on the dynamics and with Gaussian initial velocity distributions, while the positions could have an arbitrary distribution. This class of systems contains canonical equilibrium of a Hamiltonian system as a special case. We prove that for this class of systems the nth order cumulants of the initial short-time displacements behave as the 2n-th power of time for all n>2, rather than exhibiting an nth power scaling. This has direct applications to the initial short-time behavior of the Van Hove self-correlation function, to its non-equilibrium generalizations the Green's functions for mass transport, and to the non-Gaussian parameters used in supercooled liquids and glasses.Comment: A less ambiguous mathematical notation for cumulants was adopted and several passages were reformulated and clarified. 40 pages, 1 figure. Accepted by J. Stat. Phy